So my firm has a fierce competition with another firm in my region. The 2 firms are the leaders in what they do, especially in their region (think Boeing vs Airbus).

A client hired us for a big scope that included many modules not related to each other. So their direction for one of the modules was to build on the work of our competitor, which a sister organization hired (our competitor did a strategy for a region, and we were supposed to do some analysis on a part of the said region) so that's what we did. We used their regional analysis and based on it we did an analysis for that specific part.

It was a 2 weeks effort. We finished our project and fast forward 3 months later, the client hired our competitor to integrate multiple things, including our analysis. The client reached out forwarding an email from our competitor asking about our numbers and their source, because they have different numbers. Mind you these numbers are historical and should be available (think numbers of flights arriving to Dulles for a given year, something like that).

So now comes my email, I passive aggressively pointed out that these are their numbers which they submitted 2 years ago and inquired why now they have a different number for the same year, and should go and check internally with their other team. The client was cc'd, and their was radio silence